In a dairy harvesting facility, raw milk from cows is pumped through various milk conduits chillers, valves, and milk quality monitoring equipment to a bulk tank for storage. Because raw milk contains various microorganisms that have the potential to contaminate the milk conduits if those conduits are left untreated for a period of time, it is necessary to clean the milk conduits on a regular basis. It is also necessary to clean the bulk tank after a batch of stored raw milk is removed, at a time prior to that when a new batch of raw milk enters the bulk tank. Therefore, dairy harvesting facilities have washing systems for cleaning the milk conduits and bulk tanks between milkings.
A typical dairy washing system uses various liquid chemicals, such as detergents, acids, and sanitizers, along with water, to clean the milk conduits and bulk tanks. The liquid chemicals are usually dispensed in the sequence detergent/acid/sanitizer each mixed with a volume of water and circulated through the system. However, one or more chemicals can be dispensed simultaneously, so long as they are compatible, i.e., non-reactive, with each other.
The liquid chemicals are dispensed via a chemical dispenser connected to a separate source tank for each chemical to be used. Each chemical is pumped by a separate pump through an input conduit into the chemical dispenser, and exits the dispenser and travels via an output conduit to a utilization point, such as a wash vat, where the chemical can be mixed and/or diluted with water. Separate pumps and conduits are used for each chemical, to avoid unwanted reactions between chemicals during the dispensing process.
It is extremely important that the proper amount of each chemical be supplied to the utilization point for cleaning the milk conduits. If the conduits and/or bulk tank are improperly cleaned, milk passing through the conduits or into the bulk tank can become contaminated, either by microorganisms or excess chemicals in the conduits and/or bulk tank. This contaminated milk must be discarded, at considerable cost to the dairyman.
Systems have been developed to attempt to ensure that the proper amount of chemicals are used. One such system has a visual flow meter coupled to the output conduit for each chemical. Although this system allows an operator to visually verify that a liquid chemical is flowing to the utilization point, it does not allow the operator to determine whether the chemical is flowing at the proper rate. Moreover, chemical dispensers having visual flow meters are often not monitored by an operator, because the chemical dispenser, to avoid undue pressure drops, is typically located in close proximity to the chemical source tanks. These tanks, in turn, are typically located at some distance from the milking parlor, making it difficult for the operator to monitor the visual flow meter.
In an attempt to remedy these problems, an electronic flow sensor was coupled to the output conduit for each chemical. The electronic flow sensor, which was a rotometer that generated a signal corresponding to its rotation, is electrically connected to a programmable logic controller ("PLC"). The PLC is programmed to count a specific number of signals from the flow sensor, and when that number was reached, to turn off the pump. If the specific number of signals is not received in a predetermined period of time that is substantially longer than the amount of time normally necessary for the flow sensor to generate the specified number of signals, the PLC activates an alarm.
This system, while an improvement over a dairy chemical dispensing system having a visual flow sensor, still has several problems. First, since the PLC only looks for a specified number of signals, the operator cannot determine if there is a problem with the chemical dispenser, such as fouled conduits, that is slowing down the chemical flow. Second, since the alarm is only activated if the PLC does not receive the requisite number of signals in a period of time substantially longer than the normal dispensing of the chemical should take, problems that require urgent attention, such as a leak or a disconnected conduit, are not immediately detected. Finally, if the operator wants to change the number of signals counted by the PLC or the time period over which those signals are counted, he must program those changes directly into the PLC at the PLC location. This is inconvenient.
What is needed is a dairy chemical dispensing system that repeatedly monitors the actual chemical flow rate over the entire time the chemical is supposedly being dispensed, so small variations in flow rate that may indicate impending problems or the need for maintenance, as well as major problems such as leaks and disconnected conduit, can be quickly discovered and acted upon. What is also needed is a dairy chemical dispensing system than can be monitored at a location remote from the chemical dispenser itself, which also allows the operator to easily and quickly adjust the specific amount of chemical to be dispensed.
These needs are met by the dairy chemical dispenser of the present invention.